Problem: Vehicle Rod Sizing

In designing a vehicle to go down the road at 60 mph, one must know the drawbar pull of the vehicle. This is a combination of drag coefficient, rolling resistance, grade of incline, and any mechanical inefficiency. To find this information without a wind tunnel, one might use a scale of some type and pull the vehicle with a long tow-rope. Using a pneumatic cylinder with the blind end open to atmosphere and the rod end closed and fitted with a pressure gauge, we can make a nice scale that can be used to determine the horsepower. If the pneumatic cylinder has a bore of 3 inches, what would be the rod size required to have the pressure on the gauge be equal to the drag horsepower when traveling at 60 mph?

This teaser is printed in the Fluid Power Journal. Those who submit the correct answer before the deadline will have their names printed in the Society Page newsletter and in Fluid Power Journal. The winners will also be entered into a drawing for a special gift.